Power system consists of generation, transmission, distribution and consumption of electricity, and its basic task is reliable and quality supply of electricity.For years it was organized as a vertically integrated monopoly of state-owned, which ultimately proved as ineffective and cause the need of reform and liberalization of the electricity market. In many European countries the reforms have started in the nineties and required complex processes. So, the key was to follow the directives of the European Union which provided a framework for the construction of the internal market, leaving possibility each country to adopting solutions that best suit their situation.The aim of the EU is creating a single internal market in electricity. The procedures and processes defined by the legal framework are obliged to apply all EU member states. Effective solution of congestion on cross-border transmission lines is one of the very important factors that allows free cross-border exchange of electricity. The most effective method is indirect auction ie. market coupling of the electricity market. The power exchanges play a key role in connecting the electricity market and creating the single internal market for electricity EU.The Republic of Croatia has followed the processes the EU countries, the development of the electricity market has started since 2001 with the adoption of the first package of energy acts. These acts were set the bases of reforms that included the restructuring and reorganization of the energy sector, the opening of energy markets and the regulation of energy activities. The reforms were carried out in several stages. The power exchange established pursuant to the Electricity Market Act from 2013. Its goal is the establishment of organized electricity market for the day ahead and market coupling for the day ahead electricity markets in the EU.